Functional studies do not demonstrate differences in salivary flow rates between young and older healthy adults. Conversely, histomorphometric studies demonstrate about a 1/3 decrease in acinar salivary producing cells across the human life span. While many older people have dimished saliva production and complaints of a dry mouth (xerostomia). They have been attributed to systemic diseases and medications, and not to the aging process in healthy persons. Physiologists have proposed a secretory reserve hypothesis to account for the opposing findings between functional and histomorphometric studies. Our hypothesis is that young people have an excess of salivary secretory tissue which is gradually lost over the human life span. However, it has never been experimentally tested in a human model before. This study will attempt to determine if a secretory reserve exists by determining if there is a difference in how young and older healthy subjects' salivary glands respond to an anticholinergic medication (glycopyrrolate).